Steam or similar engine.



PATENTED OCT. 13, 1903.

E. THOMSON. I STEAM OR SIMILAR ENGINE.

APPLIUATION FILED APR. 3. 398.

2 SHEETS-SHBBT 1.

N0 MODEL.

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PATENTED OCT. 13, 1903.

E. THOMSON. STEAM 0B. SIMILAR ENGINE.

APPLIUATION FILED APR. 13, 1898.

2 SHEETS-SHEET 2.

I 1 1 58. '2 E55E5 sit THE NORMS warns COv. FHOYO-LITHO,, WASWNGTON, n.c,

iro. 741,388.

ll ITE Snares Patented October 13, 1903.

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ELIHU THOMSON, OF SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO GEN- ERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

STEAM OR SIMILAR ENGINE.

SPECIFICATION formingpart of Letters Patent No. 741,388, dated October13, 1903.

Application filed April 18, 1898. Serial No. 677,449. (No model.)

To all whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, in the county of Essex and State ofMassachusetts, have invented certain new and useful Improvements inSteam or Similar Engines, of which the following is a specification.

The chief object of my invention has been to improve the constructionand operation of engines to be used with steam, superheated or not,compressed air, or other gases, so as to obtain from an engine of simpleconstruction economical results in the use of steam, &c.,

which will be comparable with the results ordinarily obtained fromcomplex engines, such as ordinary compoundor compound condensingengines. I have found in the practice of my invention that engines of assmall a capac- 2o ity as from one to three horsepower may whenconstructed and operated according to my invention yield results in theeconomy of steam which, so far as I am aware, have been entirely unknownhitherto and which approach or equal the economies obtained by complextypes of engines of the compound or triple compound class of much largercapacity and which far exceed the economical results of the complexforms of engines of 0 the same capacity, and I am thus enabled to doaway with complex valve mechanisms, transfer-passages for steam,multiple cylinders of varying diameter, doc.

The principle upon which my improved 5 engine is founded issubstantially as follows: I provide a large clearance-space back of thepiston which by the instant opening of the valve when the crank is onthe dead-point and the piston down is filled almost instan- 0 taneouslywith steam up to boiler-pressure. This steam or compressed gas isexpanded rapidly during the motion of the piston forward and the supplycut off very soon after the crank passes the dead-point. In this 5manner there is an almost instantaneous filling of the clearance-spacewith steam, which is almost immediately shut 0% before the piston hasmoved through any great angle, so that the work of the engine dependsalmost altogether upon the expansion of the steam admitted to theclearance-space.

As the piston moves forward and the steam expands the power is given tothe crank almost entirely by expansion of the charge admitted, andlastly the steam is discharged through a proper exhaust-port, which maybe of any desired construction, but which as I have shown it is of thesimplest possible characterviz., a set of openings uncovered by thepiston at its extreme outward stroke. The steam left in the cylinder asthe piston returns is compressed into the clearance-space, giving anamount of compression depending upon the ratio between the volume of theclearance-space and the clearance-space plus the space traversed by thepiston. This compression-pressure will generally be a fraction of theboiler-pressure. Thus it may be fifty pounds above atmosphere while theboilerpressure is one hundred and fifty or more. I

My construction insures the separation of temperatures, inasmuch as atno time does the steam reverse its progress or direction of movement inthe cylinder between admission and exhaust. The admission end of thecylinder therefore can remain at the temperature of the steam ofadmission, while the exhaust portion of the cylinder is at a lowtemperature-that of the steam cooled by expansion in the abstraction ofwork in moving the piston. In the same way there is no possibility ofcondensed water or the cooled products after expansion being thrown backupon the hot end or admission end except what is demanded forcompression, in itself a heating process. The cylinder at the end ofeach power-stroke is cleared of cooled and condensed products, such ascondensed water. The exhaust-ports being situated as far as possiblefrom the inlet-ports they do not 0 share each others temperature. It isto these and other features of construction to be pointed out to which Iattribute the high economies of steam which I have obtained forsmall-powered and simple engines.

I am enabled by simple means to obtain a compound effect, and so furtherincrease to a certain degree the economy.

My invention relates chiefly, therefore, to engines of simple characterwhereby the efzoo fects of expansion and compounding-are obtainedwithout the necessity for the complexity of compound engines. The usualexpedients of non-conducting lagging or steam-jacketing may be resortedto to protect the cylinders from external cooling. I find, however, thatany plain non-conducting lagging is generally suflicient.

Figures 1 and 2 are plan and elevation, respectively, of a compoundengine embodying the features of my invention. Figs. 3, 4, 5, 6, and 7are diagrammatic views of the parts of the engine shown in Figs. 1 and2. Fig. 8 is a modification in the manner of operating theadmission-valve.

Referring first to Figs. 1 and 2, two pistons (which may be of differentsizes) P and P are provided with suitable cranks set relatively to eachother, so that piston P leads piston P in revolution by, say, ninetydegrees up to one hundred and twenty degrees,

as may be selected. Admission to cylinder 0, which may be called thehigh-pressure cylinder, is made into a large clearance-space oruntraversed space at the back when piston P is down. The valve V is shutsoon after the crank to piston P passes the deadcenter. The steam inexpanding pushes piston P forward and uncovers port E, which admitsequalization of pressures between the two cylinders O and 0 back oftheir pistons. This occurs, preferably, at a point some fifty degrees orsixty degrees of revolution of the crank of piston P before reaching theouter dead-center. The steam from C then follows piston P outwardly,while piston P returns, covers exhaust-port E, and compresses what steamremains in cylinder Oafter such covering of E preparatory to receipt ofnew steam through valve V into the clearancespace. In cylinder C thereneed be but little clearance-space. The steam taken over from cylinder 0goes on expanding in C until piston P is fully out. i

It will be seen that no exhaust-valve is provided for the low-pressurecylinder, the exhaust being controlled by the motions of the pistonsthemselves. This greatly simplifies the construction and leaves only asingle valve V to be operated for a compound ongine. The construction isas follows: The communicating ports E for transferring the steam fromcylinder 0 to cylinder 0 are arranged so as to be uncovered not only atthe extreme outward stroke of piston P, but also for a similar period.on the extreme inner stroke of said piston, the said piston P being madeshort enoughto permit this. There are also provided exhaust-openings E,which are uncoveredby piston P at its extreme outer position, as shownin Fig. 1.

The operation will be better understood by reference to Figs. 3, 4, 5,6, and 7, which are simply diagrammatic views of the parts in the engineof Figs. 1 and 2 at different times of revolution. In Fig. 3 theadmission steamvalve V is open and the clearance-space back of piston Pis filling with steam, while the crank corresponding thereto is just atdeadcenter or a little beyond. Meanwhile since the crank moved by pistonP follows crank of piston P at right angles, or thereabout, piston P isat its most rapid rate of motion inward and is discharging steam throughport E, which has been uncovered by piston P in its backward stroke.Valve V closes and piston P moves forward, as in Fig. 4, but beforereaching the center communicates with cylinder C through port E just aspiston P begins its forward motion, as indicated. Both pistons aremoving forward in this case with the port E open between them and steampassing from cylinder 0 to cylinder 0 This is continued, as in Fig. 5,while the crank of piston P is passing over its outward deadcenter,piston P making its elfective forward stroke meanwhile. Finally port E,which remained open, is closed by the backward motion of piston P, as inFig. 5, and piston P I l is ready to open exhaust-port E and so drop thepressure back of piston P to atmosphere or below when condensers areemployed.

Fig. 6 shows piston P nearly completing its backward strokeand'openingport E to the atmosphere or condenser from cylinderspace in 0 whilepiston P has started back ready to expel what remains in cylinder Gthrough port E to atmosphere or condenser. This expulsion goes onthrough stage Fig. 3 while valve V is open and is completed in the stage(shown in Fig. 7) intermediate between that of Fig. 3 and Fig. 4, wherepiston P has begun its outward stroke and piston P is just aboutcompleting its inward stroke. Piston P is shown as justhaving coveredthe port E in its outward stroke in Fig. 7, while piston P now onfurther motion compresses what slight amount of steam remains into itsown clearance -space, which is preferably made only slight, as abovestated. I am thus enabled to secure the effects of compounding in asimple type of construction of engine.

Where the initial movements of the piston in my engine are given byextraneous power, as by turning over the crank at the start, I maydispense with mechanism for operating the valve V even and cause thepiston itself to work the valve, it being only necessary that the valveV shall open for a short interval while piston P is nearly at rest onthe inner dead-point. In Fig. 8, Ois the cylinder, as before, P thepiston, and V is avalve the stem of which projects inward toward thepiston, so as to be struck by the piston and opened for a short intervalas the piston is almost down orwhile the crank is passing thedead-center. This admits steam to the clearance space S while said crankis on dead-center and fora very short interval before and after thatpoint is reached. The opening of valve V thus becomes automatic, and thesteam is exhausted at port E, as before. This arrangement is usefulwhere the engine is to run at a determined speed once having beenstarted, as in driving dynamos for electric lighting. To lessen the blowof the piston in opening valve V in running at good speed, the ends ofpiston P may be bored out into a small cylindrical cavity and a disk orpiston inserted therein which engages with the valve-stem. A smallamount of fluid in the space so provided between the small piston orvalve-operating piston and the large piston proper acts to damp the blowstruck on the valve-stem. A spring Q may also be provided, holding backthe small piston 12 to a definite position when not engaged with thevalve-stem.

In describing the engine of my invention no means of governing thespeed'have been described or shown, it being understood that variousmeans of governing may be employed where itis necessary that the engineshall be given a regular speed. Thus centrifugal throttie governors maybe used to throttle the steam, or the engine may be governed on thehit-and-miss principle, as with gas-enginesthat is, the valve whichadmits steam may be caused bythe governor to intermit in its openingwhen it tends to be accelerated beyond normal speed-and thisintermission may be put under the control of centrifugal or othergovernors similar to those used in gas engines.

With simple engines of as low as three to five horse-power constructedsubstantially as in Figs. 1 and 2, giving a compression of about fiftypounds and with a boiler-pressure of two hundred pounds dry steam, abrake horse-power can be expected to be obtained with an expenditure ofabout twenty pounds per horse-power hour, the speed of the engine beingbetween six hundred and seven hundred revolutions per minute.Considerably better results can be obtained with larger engines, whilemy invention secures also a relatively high light-load efficiency ascompared with complex forms of compound engines.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. In a compound engine, the combination of a high-pressure cylinder; alow-pressure cylinder; ports in the high-pressure cylinder which admitsteam to the low-pressure cylinder when uncovered by the forward movement of the piston, and exhaust the low-pressure cylinder when uncoveredby the backward movement of the piston, additional exhaust-ports for thelow-pressure cylinder which are uncovered by the forward movement of thelow-pressure piston, and a valve controlling the admission of steam tothe high-pressure cylinder.

2. In a compound engine, the combination of a high-pressure cylinder, alow-pressure cylinder, a plurality of exhaust-ports formed in thehigh-pressure cylinder which are uncovered at each end of the stroke ofthehighpressure piston but are unaffected by the movements of thelow-pressure piston, a plurality of exhaust-ports which are formed inthe low-pressure cylinder and are covered and uncovered by the movementsof the lowpressure piston, an outwardly-opening puppet-valve admittingsteam to the cylinder, means driven by the engine for opening the valve,and an automatic device for closing the valve.

In witness whereof I have hereunto set my hand this 11th day of April,1898.

ELIHU THOMSON.

Witnesses:

DUGALD MCKILLOP, HENRY O. WESTENDARP.

